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The present invention relates to seed planting assemblies in general, and in particular relates to a method and apparatus for selectively disengaging seed planting units of a seed planting assembly.
Seed planting units generally include a laterally extending tool bar that supports a plurality of parallel planting units (also known as row units). The tool bar is typically coupled to a tractor or like vehicle suitable for towing the planting assembly along a field that is to be seeded to a crop. Each planting unit includes a device for opening a seed trench in the ground as the tractor draws the tool bar across a field to be seeded. Each planting unit further includes a seed meter to dispense seeds at a controlled rate into a seed trench as the meter is advanced above and along the seed trench during operation. Generally, seeds are delivered to the metering assembly from a seed hopper located on the planting unit or, alternatively, from a smaller container fed from a centralized large hopper used to feed all or a portion of the planting units. Each planting unit further includes a closing assembly that moves soil at the sides of the seed trench to close the seed trench over the planted seeds. Adjacent planting units are laterally spaced a sufficient distance to form seed trenches that are spaced a corresponding distance apart that is suitable for the type of seed being planted.
It should be appreciated that a crop yield is maximized when all seeds emerge from the soil within a given timeframe relative to each other. Otherwise, if some seeds emerge later than others in a given row, the yield for that row can be substantially reduced. One known method for encouraging uniform seed emergence is to maintain the seed trench at a constant depth when performing seed planting operations. Seed trench depth is typically controlled by one or more gauge wheels that ride along the ground and have a predetermined vertical position relative to the seed trench opening device.
During operation, several factors can affect the depth of the seed trench, including, for instance, the soil type, pre-tillage applied to the soil, soil moisture, amount of residue covering the soil, residue moisture, previous crops, opener blade wear. These variables can change from field to field, and furthermore typically change within a single given field. Another factor which significantly affects the seed trench depth is the speed of the planting operation, it being appreciated that faster travel causes the opener blade to ride up in the ground, which decreases the seed trench depth.
Conventionally, uniform seed trench depth was attempted by including a mechanical spring member in planting units that delivers a downward force (down pressure) on the planting unit. The spring force can be increased or decreased to correspondingly increase or decrease the down pressure on the planting unit gauge wheels when the unit travels over hard and soft ground, respectively. The adjustment of down pressure, along with the gauge wheels, controls the depth of the seed trench-opening device, thereby maintaining the seed trench at a relatively constant depth during operation. It should be appreciated that an insufficient amount of down pressure causes the vertical position of the seed trench-opening device to vary, while an excessive amount of down pressure unnecessarily forces the gauge wheels to compact the ground adjacent the seed trench, thereby retarding growth in the row. While manual adjustment mechanisms proved adequate to adjust down pressure, they required the operator to stop the tractor, exit the vehicle, and adjust the downpressure on each individual planting unit. This method incorporates several disadvantages, including operator inconvenience and the potential for operator error.
Accordingly, automatic down pressure adjustment systems have been introduced that include a strain gauge for measuring the forces on the row unit gauge wheels. The strain gauge provides an output to a microprocessor which, based on the measured strain, provides a signal to an actuator that increases or decreases the applied down pressure, depending on the measurement of the strain gauge. Strain gauge-based down pressure systems, while alleviating some of the inconveniences imposed by the manual system, nonetheless are themselves inconvenient to operate. For instance, strain gauges must be constantly calibrated, and are subject to error. Furthermore, the inclusion of a microprocessor adds cost and complexity to a mechanical system.
What is therefore needed is a simplified and more reliable method and apparatus for automatically adjusting the pressure acting on the planting unit during operation as the planting unit travels between areas of hard and soft soil.
In accordance with one aspect of the present invention, a seed planting assembly includes a planting unit frame that is supported by a laterally extending support member. The planting unit frame carries a seed trench opening assembly operable to create a seed trench in a ground surface. The planting unit frame further carries a seed delivery assembly delivering seeds into the seed trench. The planting unit frame further carries a seed trench closing assembly operable to close the seed trench. A depth regulating member is provided having a vertical position relative to the seed trench opening assembly. The depth regulating member experiences an actual vertical force that controls ground surface engagement. A spring is supported by the support member and connected to the planting unit. The spring provides a variable spring force against the frame in response to variations in internal spring pressure. A pressurized fluid source is provided and operable to provide fluid to the spring. A valve links the fluid source to the spring. The valve is in mechanical communication with the seed trench opening assembly and enables fluid to flow in and out of the spring to correspondingly adjust the spring force when the actual vertical force differs from a desired vertical force.
The foregoing and other aspects of the invention will appear from the following description. In the description, references are made to the accompanying drawings which form a part hereof, and in which there is shown by way of illustration, and not limitation, a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention, however, and reference must therefore be made to the claims for interpreting the scope of the invention.